An umbilical consists of a group of one or more types of elongate active umbilical elements, such as electrical cables, optical fibre cables and fluid conveying conduits, cabled together for flexibility and over-sheathed and/or armoured for mechanical strength. Umbilicals are typically used for transmitting power, signals and fluids (for example for fluid injection, hydraulic power, gas release, etc.) to and from a subsea installation. The main fluid conduits used for manufacturing umbilical are thermoplastic hoses and steel tubes. API (American Petroleum Institute) 17E “Specification for Subsea Umbilicals”, third edition, July 2003, provides standards for the design and manufacture of such umbilicals.
A steel tube umbilical is defined as an umbilical wherein all or most of the elongated umbilical elements which compose the umbilical are steel tubes. The steel tubes and the other elongated umbilical elements that make up the umbilical are grouped together and wound in a helical pattern. Examples of steel tube umbilical are disclosed in the documents U.S. Pat. No. 6,472,614, WO93/17176 and GB2316990. Steel tubes are not permeable to gases. They are also able to resist installation and in-service axial loads, and high external collapse pressures; therefore the umbilical, with judicious design, is able to withstand axial loads without requiring the addition of tensile armour layers. It is also possible to increase further its axial resistance by adding internal steel or composite rods inside the bundle (for example see U.S. Pat. No. 6,472,614 and WO2005/124213).
Flexible pipelines are used in the offshore industry for transporting, over long distances, a fluid that is under pressure and possibly at a high temperature, such as gas, oil, water or other fluids. Such flexible pipes generally comply with the standard: API 17J “Specification For Unbonded Flexible Pipe”, second edition, November 1999. The unbonded pipe construction consists of separate unbonded polymeric and metallic layers, which allows relative movement between layers.
U.S. Pat. No. 6,102,077 discloses an elongated subsea structure combining the functions of a flexible pipe and of an umbilical. This structure comprises a large diameter central flexible pipe being used as a production line for conveying oil or gas, and a plurality of small diameter peripheral pipes arrayed in helical or S/Z manner around the central flexible pipe, said peripheral pipes being used as service or control lines for fluid injection, gas lift injection, hydraulic power or gas release. Such structures are marketed by the Applicant under the Registered Trademark ISU® (“Integrated Subsea Umbilical”) and the identifier IPB (“Integrated Production Bundle”).
The invention aims at solving the problem of joining the axial load carrying components of the elongate structure with a termination or end fitting. The axial load carrying components can include:                The tensile armour layers for cables, flexible pipes and some umbilicals;        The steel tubes of steel tubes umbilicals, ISU® and IPB;        The steel or composite rods used to increase the axial load bearing resistance of umbilicals.        
The axial tensile loads acting on the assembly of the elongated subsea structure and the termination can for many applications be very high. The joint between the axial load carrying components and the termination has to be provided with sufficient strength to withstand such great axial tensile loads acting thereon.
It is known, when the axial load carrying components are metallic, to weld such components directly to a bulkhead provided on the termination. However, the welding process is very time consuming, costly and labour intensive, and may harm polymer layers by heat from the welding, such as electrical sheathing and insulating materials around conductors.
Furthermore, this solution does not fully prevent the radial displacements of the load carrying components within the termination. To overcome that drawback, a known improvement consists in filling the termination with a hard-setting compound, such as an epoxy resin. In this application, the hard-setting compound is used to prevent straightening of the tubes i.e. to prevent radial displacement within the termination. Tensile loads are transmitted through the steel tubes to the bulkhead plate to which they are welded, thus the hard-setting compound does not have to withstand the primary axial loads.
To avoid or overcome the drawbacks of the welding solution, it is also known to modify or deform the end part of each load carrying component and then secure said end parts in a cavity within the termination filled with a hard-setting compound, such that said end parts are embedded in the hard-setting compound.
U.S. Pat. No. 6,412,825 discloses a solution for joining the tensile armour layers of a flexible pipe with an end fitting, where the tensile armour layers are made with rectangular steel wire and where the end part of each wire is twisted before being embedded in the hard-setting compound.
U.S. Pat. No. 6,161,880 discloses a second similar solution for joining tensile armour layers, where the end part of each steel wire is formed in wave shape before being embedded in the hard-setting compound.
FIG. 2 of U.S. Pat. No. 4,640,163 discloses a third similar solution for joining the tensile armour layers of an umbilical with a termination, where the end part of each steel wire is formed in hook shape before being embedded in the hard-setting compound.
However, these solutions, based on securing the load carrying components in a cavity filled with a hard-setting compound, may also overheat temperature sensitive components (such as polymer sheaths), especially for large diameter umbilicals or flexible pipes where the cavity to be filled with a hard-setting compound has a large volume, because of the exothermic curing reaction. Furthermore, difficulties in pouring large volumes of such hard-setting compound may induce defects such as air bubble entrapment, with detrimental effect on the anchoring resistance. Another drawback in the case of large volumes is shrinkage of the hard-setting compound during the curing that may induce detrimental stresses in the termination, and may reduce the hard-setting compounds ability to withstand compressive loading and allow compound and/or component movement within the termination.